(a) Field of the Invention
The following disclosure relates to a method for preparing an electrode active material for a rechargeable lithium battery, an electrode active material for a rechargeable lithium battery, and a rechargeable lithium battery.
(b) Description of the Related Art
A rechargeable lithium battery has recently become prominent as a power supply for portable small electronic devices. The rechargeable lithium battery has a discharge voltage of two times higher than an existing battery using an aqueous alkaline solution by using an organic electrolyte solution. As a result, the rechargeable lithium battery provides higher energy density than the existing battery.
As a cathode active material for the rechargeable lithium battery, an oxide formed of lithium having a structure in which intercalation of lithium ions is possible, such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), or the like and a transition metal is mainly used.
As an anode active material for the rechargeable lithium battery, various types of carbon materials including artificial graphite, natural graphite, soft carbon, and hard carbon are mainly used. As the anode active material for the rechargeable lithium battery according to the related art, a crystalline-based carbon material such as artificial graphite or natural graphite in which intercalation/deintercalation of lithium ions is possible has been mainly used. In the case of the carbon material, a competitive cost and an initial discharge capacity are excellent. However, the rechargeable lithium battery market has been expanded to ESS or the field of electric vehicles, such that the development of a high-stability anode active material to be available at a low temperature has been demanded. As one of methods for solving it, a study on an anode material with ceramic coating has been conducted.
Generally, the ceramic coating is formed by a wet method, and it has been confirmed that high reversible capacity and cycle characteristics are improved by coating silica on a surface of the natural graphite through a hydrolysis method of tetraethyl orthosilicate (TEOS) using a sol-gel process (Trans. Nonferrous Met. Soc. China 17 (2007) 1339).
Furthermore, describing Patent Documents (Application Nos. 10-2009-0051627 and 10-2009-0045873) in which the ceramic coating is formed by a dry method, it may be confirmed that thermal stability and efficiency according to the charge and discharge and cycle life characteristics of the battery are improved. However, with the ceramic coating method, the surface is not uniformly coated and the ceramic is partially coagulated.
Therefore, according to the demand of the rechargeable lithium battery market, a simple process capable of mass-production of the ceramic coating active material for a middle and large-sized battery and the development of a uniform ceramic coating technology capable of reducing deviation between the ceramic coagulation and the active material have been demanded.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.